Tutorial: Holographic Radio: A New Paradigm for Communication and Sensing in 6G Part 2

This tutorial focused on holographic radio, which integrates massive antenna elements into a compact space to achieve ultra-massive MIMO for high resolution sensing and high-capacity communications, has been considered as a promising enabling technique for the forthcoming sixth generation (6G) networks. Widely-utilized phased arrays relying on costly components make the implementation of ultra-massive MIMO in practice become prohibitive from both cost and power consumption perspectives. In contrast, the recent developed reconfigurable holographic surfaces (RHSs) composing of densely packing sub-wavelength meta material elements provide a new method to solve the above issue without costly hardware components. By leveraging the holographic principle, the RHS serves as an ultra-thin and lightweight surface antenna integrated with the transceiver, thereby providing a promising alternative to phased arrays for realizing ultra-massive MIMO. In this tutorial, we will first provide a basic introduction of RHSs. We then introduce the unique features of RHSs which enables both communication and sensing, in a comprehensive way. Related design, analysis, optimization, and signal processing techniques will be presented. Typical RHSbased applications for the wireless communications and radio-frequency sensing will be explored. Our implementation of RHSs as well as the developed prototypes of communication and sensing systems will also be reported. Several up-to-date challenges and potential research directions will be discussed as well.